Thread control device for sewing machines

ABSTRACT

An improved thread control mechanism for sewing machines adapted to minimize breakage and entanglement of the needle thread in a two-thread sewing machine, and which insures the formation of a uniform and desirable line of stitching at high speeds of operation. It is particularly advantageous in connection with a lockstitch sewing machine, which at one stage in a cycle of operation of the machine must subject said thread to a quick take-up action when a loop of the thread has been passed around half of the circumference of a bobbin case. The improved mechanism eliminates the need for a coiled check spring which heretofore has been provided to present an arm in the path of movement of the thread after it leaves a thread tensioning device. By eliminating the need for the check spring, the extent of movement of a thread eyelet at the outer end of a take-up lever is reduced, from the extent that was required in prior constructions involving a check spring. A plurality of cams are provided on a shaft which is rotated at the same speed as the main drive shaft of the sewing machine. These cams act upon different portions of the needle thread as the latter passes through a succession of eyelets provided on certain prongs of rockable members. Normally these members are retained in an active position, but they are shifted to an inactive position upon the lifting of the pressure foot. The thread control means of the present invention exercises the desired control over the needle thread when the machine is used on a variety of types of work which have normally, heretofore, required special adjustments and even changes in the mechanism when variations in the thickness and the nature of the work pieces being dealt with are involved.

United States Patent 3,683,832 1 Aug. 15, 1972 Schoij [54] THREADCONTROL DEVICE FOR SEWING MACHINES [72] Inventor: EdgarSchoij,Hinsdale,lll. [73] Assignee: Union Special Machine Company,

Chicago, 111.

22 Filed: Sept.4, 1970 211 Appl.No.: 69,556

3,140,682 7/1964 Hale et al. ..l12/242 Primary Examiner-Patrick D.Lawson Attorney-John A. l-lowson 5 7] ABSTRACT An improved threadcontrol mechanism for sewing machines adapted to minimize breakage andentanglement of the needle thread in a twothread sewing machine, andwhich insures the formation of a uniform and desirable line of stitchingat high speeds 31b 3 25b 21 24b an arm in the path of movement of thethread after itleaves a thread tensioning device. By eliminating theneed for the check spring, the extent of movement of a thread eyelet atthe outer end of a take-up lever is reduced, from the extent that wasrequired in prior constructions involving a check spring. A plurality ofcams are provided on a shaft which is rotated at the same speed as themain drive shaft of the sewing machine. These cams act upon differentportions of the needle thread as the latter passes through a successionof eyelets provided on certain prongs of rockable members. Normallythese members are retained in an active position, but they are shiftedto an inactive position upon the lifting of the pressure foot. Thethread control means of-the present invention exercises the desiredcontrol over the needle thread when the machine is used on a variety oftypes of work which have normally, heretofore, required specialadjustments and even changes in the mechanism when variations in thethickness and the nature of the work pieces being dealt with areinvolved.

24 Claims, 10 Drawing Figures PATENTEDAUB 1 5 I972 SHEET 2 [IF 6PATENTEUAUG 1 5 m2 SHEEI 3 [If 6 PATENTEIH I973 3.683.832

sum 5 OF 6 FIG] THREAD CONTROL DEVICE FOR SEWING MACHINES This inventionrelates to mechanism for controlling the delivery of the desiredamountof thread to the stitch forming mechanism of a high speed sewingmachine, and the application of a reasonably high tension to the threadat the time a stitch is being completed to insure the formation of agood stitch. A positively driven cam arrangement is provided for thispurpose.

The invention has been developed, and is disclosed herein, in relationto a lockstitch sewing machine which is intended for high speedoperation, at speeds of 5,000 to 7,000 R.P.M. or even higher. Heretoforeit has been found difficult to control the delivery of the desiredamount of thread and to insure uniform stitch formation, with thestitches being soft but firmly gripping the materials being sewntogether, without danger of producing puckering of the material, in theoperation of the machine at such high speeds.

Certain aspects of the invention are capable of advantageous use inrelation to a variety of types of sewing machines, but it has beenspecifically developed to overcome certain problems encountered in theoperation of a lockstitch machine at high speed. Accordingly it is beingdisclosed herein in relation to such a machine.

One problem presented in connection with the operation of a lockstitchmachine at high speeds is that the needle thread mustQat times duringeach cycle of operation of the machine, be supplied in sufficient amountin the stitch forming region to enable the passage of a loop of saidthread around the bobbin case, which revolves at high speed in theregion below the throat plate of the machine. It is then necessary topull the thread upwardly, into engagement with the under surface of thework, with a sufficient tension to bring about the desired stitchformation at the high speed of operation of the machine.

Heretofore it has been considered necessary to pro vide a coiled checkspring which has an arm positioned in the path of movement of the threadas it leaves a thread tensioning device and is being delivered towardthe eye of the needle. Such a coiled check spring has, however, beenfound to create further problems in the correct handling of the threadin a high speed stitching operation. Accordingly, the present inventionserves to eliminate the need for the provision of a coiled check spring,and it provides a thread tensioning device which is of such characterthat a proper tension will be applied to the needle thread at the time astitch is being affixed to the work. This serves to insure the formationof a firm line of stitching without any danger of producing puckering ofthe work material in the course ofthe stitching operation.

Toward the foregoing end the present invention incorporates a pluralityof thread take-up means in the path of movement of the thread, thesetake-up means being active at the appropriate time during each stitchforming cycle to insure the proper formation of a seam. In thisconnection, the present invention includes a take-up lever including aneyelet through which the needle thread passes and which is rockableduring a certain part of a stitch forming cycle, this take-up leverthereby imparting a take-up action to the thread after it has beenpassed around to the 6 oclock point of the bobbin case, so as to pullthe needle thread thus released up into a position in which it will notbecome entangled with itself or with other thread. Such a takeup leverhas been provided heretofore, as disclosed in the I-Iale et al. US. Pat.No. 3, l40,682 granted July 14, I964. However, in accordance with thepresent invention it has not been found necessary to impart as great atake-up action to the lever mentioned as was required in accordance withthe disclosure of the specified patent.

Through the provision of a plurality of pronged eyelet members along thepath of movement of the thread from a source of supply to the needle,and the provision of cam means cooperating with the thread in regionsbetween the eyelets of said members, in accordance with the presentinvention, it has been found possible to reduce the extent of movementof the eyelet of the take-up lever in the course of the stitchingoperation. Toward the same end, the present invention eliminates theneed for the coiled check spring having an arm in the path of thethread, as shown at 50d in said Hale et al. patent. These aspects of theinvention have been found to insure the desired uniform formation of theline of stitching, which has not been possible in the high speed seamingof certain types of work in the past.

With the foregoing features and. advantages of the invention in mind, anillustrative embodiment of the same will now be described in somedetail. For this purpose the invention has been illustrated herein andwill be described as applied to a lockstitch sewing machine of thecharacter disclosed in said Hale et al. patent. Referring now to thepresent drawings:

FIG. I is a front elevational view of themachine in question with aportion of the frame broken away in the region of the needle head;

FIG. 2 is-an end elevational view of the machinev as seen from the leftof FIG. 1, with a cover plate for the needle head removed;

FIG. 3 is a detail view, in elevation, showing a portion of the upperarm of the frame of the machine with a thread supply sourceschematically indicated and with certain elements of the thread controlmeans shown;

FIG. 4 is a detail view, in horizontal section through the upper arm ofthe machine frame, and shows various elements of the thread controlmeans of the present invention;

FIG. 5 is a vertical sectional view taken along the plane S-S of FIG. 3;

FIG. 6 is an elevational view of a part of the upper arm of the frame ofthe machine with a portion of this broken away to illustrate certaindevices within the arm;

FIG. 7 is a detail view in horizontal section through certain adjustableparts of the mechanism shown in FIG. 4;

FIG. 8 is a vertical sectional view along the line 88 of FIG. 4;

FIG. 9 is a detail view, in plan along the line 9-9 of FIG. 5, showingcertain elements of thread guiding means; and

FIG. 10 is an exploded perspective view of certain parts incorporated inthe machine for imparting a takeup action to the needle thread.

As stated above, the invention hasbeen shown herein as applied to alockstitch sewing machine of the type disclosed in the I-Iale et al.patent and in certain earlier patents referred to therein. The frame ofthe machine has a base portion 1 which is provided with a worksupporting surface, a vertical standard 2 rising from one end of thebase portion, and an overhanging arm 3 extending from the upper portionof the vertical standard in a direction substantially parallel to thebase portion 1. The overhanging arm has a head portion 4 in which avertically reciprocatory needle bar and also a presser bar are mounted.Suitable connections from a power source are provided to a combined handwheel and pulley 5 secured to the main drive shaft 6 which extendlongitudinally of the overhanging arm 3. Within the base portion 1 ofthe frame there is provided conventional work feeding means andcomplementary stitch forming means of a well-known character. Thus, asshown in FIG. 2, there is provided a feed dog 7 which is carried by afeed bar that has a downwardly extending portion 8 with suitableconnections from a shaft within the work supporting portion of theframe, which shaft is connected in a conventional manner with the maindrive shaft 6. The rotary hook 9 is driven by suitable connections fromthe shaft within the base of the frame and it is driven insynchronization with the reciprocation of the needle bar, but it rotatesat twice the speed of the main shaft. The work is held against the topsurface of the work supporting portion of the frame by a presser foot 10which is mounted on a vertically movable presser bar 10a and is adaptedfor rocking movement to a certain extent as the work is fed through themachine. The presser bar is mounted for sliding movement within a sleeve10b carried by the needle head of the frame, and it is urged downwardlyby a spring 100 within the needle head. The lower end of this springcooperates with an arm 10d secured to the presser bar. Conventionalmeans are provided for varying the force of the spring 100 in urging thepresser foot against the work support and the feed dog 7.

Since the present invention is primarily concerned with the threadcontrol means which cooperates with the needle thread, this will now bedescribed in detail. As shown in FIG. 3 the thread T to be delivered tothe needle is supplied by a suitable source C, from which it isdelivered to a thread tensioning device carried by a bracket member Bmounted on top of the overhanging arm 3 of the frame. This threadtensioning means is provided with a manually adjustable head 12 which,by turning in one direction or the other, may vary the force of a spring12a which urges an upper disk 12b downwardly toward a lower disk 120.The thread from the supply is passed between the disks 12b and 120 andis guided for this purpose by eyelet members 11 and 13 secured to thetop of the bracket member B. From the eyelet of member 13 the thread ispassed downwardly to the thread control means 21 of the presentinvention. In the region of the control means 21 the thread is firstpassed through an eyelet in a prong 14a of an element 14 which issecured to a sleeve 56a that is rockably mounted on a rock shaft 35(FIG. 4). From this point the thread is passed to and through an eye ina prong 14b of the element 14, and from here successively throughopenings in prongs 15c, 15b and 15a of an element 15 which is secured tothe rock shaft 35.

From the hole in prong 15a of element 15 the thread is passed downwardlyaround a hub portion 300 (FIG. 5) of a cam member 30 which is secured bya screw 300 to a rotary shaft 22. After passing through a suitable arearound the periphery of hub 300 the thread is passed downwardly andtoward the left (FIG. 3) to an eyelet in a vertically adjustable member16 carried by the needle head of the sewing machine frame. From thispoint the thread extends upwardly to and through an eyelet in a rockablelever 17 which serves as a thread take-up member. From the latter thethread extends downwardly to and through an eyelet in an element 18connected with a needle bar bushing 19 which extends downwardly to acertain extent from the needle head. The needle 20a is carried by aneedle bar 20 which is reciprocated vertically within the bushing 19 fora suffi-,

cient distance to carry the point of the needle from a lo cation abovethe work to a position beneath thethroat plate 1a (FIG. 2) of the worksupport 1. As will be understood, the thread now extends from the laststitch in the work piece, to the eye of the needle, and when the latterstarts its upward movement a loop projects from the under side of thework piece and this is then seized by the beak of the rotary hook 9 andis carried by the latter around the thread extending from the bobbincase of the hook to the under side of the work, thus forming a newstitch.

Suitable connections are provided for rocking the take-up lever 17 toalternately pull up the needle thread to complete a stitch and to freethe thread to enable a loop of the same to be carried around the bobbincase by the rotary hook 9. The connections for this purpose are of thegeneral character disclosed in the US. Pat. to Covert No. 2,977,9l0granted Apr. 4, l96l. Such connections are driven by a rotary membersecured to the main drive shaft 6 of the machine.

Cooperating with the needle thread in the region in which it passesthrough the openings in the extensions of members 14 and 15 are aplurality of cam elements 30a, 30b, 31a and 31b. As best shown in FIG. 4the cam elements 300 and 30b are in spaced relation, so that theenlarged portion 30a cooperates with the thread passing between prongs15a and 15b, while the enlarged portion 30b of element 30b cooperateswith the thread passing between prongs 15b and 156. The two cam elements31a and 31b are close together and they are rotated to carry theirenlarged portions 31a and 31b between prongs 14a and 14b of member 14.The purpose of providing the two cam elements 31a and 31b is to enablevariation in the circumferential length of the combined enlargedportions thereof which act upon the thread passing between prongs 14aand 14b. This provides for any adjustment that may be desired to conformwith the nature and thickness of the work pieces being dealt with at aparticular time.

Suitable connections are provided from the main drive shaft 6 of themachine for imparting a revolution to each of the camming elements 30a,30b, 31a and 31b on each revolution of the main shaft. Theseconnections, as best shown in FIG. 4, involve a helical gear 26 securedto the shaft 22 that cooperates with a helical gear 27 secured to themain drive shaft, which gears have a 1:1 driving ratio. Shaft 22 isjoumalled in a sleeve 23 which is carried by a member 24. The latter isformed with a bushing type portion 24a and a flange some adjustment ofthe angular position of the member 24 within the frame, the flange 24bis provided with slightly elongated openings 24c (FIG. 1) through whichthe screws 25b extend. The various cams a,30b, 31a and 31b are retainedon the shaft 22 by screws 30e and 316 which cooperate with hub portions300 and 310 of the respective members 30 and 31. At the outer end of theshaft 22 there is provided a cap 32 the inner circumferential surface ofwhich engages the cam 31b, and it is firmly retained in position bymeans of a screw 33 which fits into a threaded opening in the end ofshaft 22 (FIG. 5). For retaining the rock shaft 35 against movement inan axial direction it is provided with a I groove in which is placed aC-washer 36 (FIG. 4). This fits into a small depression in the outerface of the front wall 50a of the overhanging arm 3 of the machineframe. Movement of the shaft 35 axially in the opposite direction isprevented by means of a lever 38 which is secured to the shaft by ascrew 39 (FIGS. 4 and 6). A washer 37 is fitted onto the shaft 35 withina depression in an intermediate wall 50b of the arm 3 and cooperateswith the lever 38 and screw 39 in retaining the shaft 35 against axialmovement in said opposite direction.

Rock shaft 35 is urged into the position shown in FIG. 6 by a coilspring 44 which has one or more turnsaround the shaft 35, and has one ofits ends engaged with the bottom of overhanging arm 3 and its other endhooked beneath the free end of lever 38. The spring thus urges the freeend of said lever against a stop screw or pin 45.

All of the cams 30a, 30b, 31a and 31b upon rotation with the shaft 22serve to take-up some length of the needle thread as the outwardlyextending portions of these cams move into the passages provided betweenthe prongs of the members 14 and 15. The extent of the take-up actionimparted by the various cams may be varied by selection of cams ofdifferent sizes. Also such takeup action can be varied by changing theangular disposition of the eyelet carrying members 14 and 15 in relationto a horizontal plane extending through the axis of the shaft 35 and asleeve 56a. This can be accomplished by loosening screws Me and 15e,respectively, and then retighten those screws when the desired positionof the members 14 and 15 has been achieved. With respect to the camformed by elements 31a and 31b, the duration and extent of their actionupon the thread extending between the prongs 14a and 14b can be variedby changing the relationship of certain parts shown in FIGS. 4, 7, 8 and10. This involves the provision of a shoulder screw 57 which has anenlarged portion of its stem slidably fitted within an opening 56cprovided in lever arm 56b connected with the sleeve 56a. The end ofscrew 57 has threaded engagement with an opening 58a provided in awasher-like element 58 which surrounds a reduced diameter portion of astud 59. The opening 580 is off center in relation to the axis of thestud 59, the latter being journalled in an opening 600 provided in abracket plate 60.

The opening 60a is located adjacent one end of the plate 60, which is oflarger dimension than the opposite end of this plate. Adjacent the outerface of the plate 60 there is provided a spring washer 61 whichsurrounds the stud 59, and outwardly of this there is provided a knurledknob 62 which is secured to the stud by a screw 63. Plate 60 is providedwith a suitable opening 60b on its inner face which fits over the end ofthe rock shaft 35 and is secured thereto by set screws 64. The knob 62is provided with a radially extending flange which carries markings,such as indicated at 62a, which in conjunction with a mark 66 providedon the outer face of the member 60 gives an indication of the setting ofthe knob. It is to be noted that the axis of opening 58a in the element58 is shown in FIG. 10 as being located in the same horizontal plane asthe axis of the stud 59. By this arrangement, rotation of the knob 62will be effective through in one direction or the other from theposition shown to bring about the desired position of member 14.

The shaft 35 is adapted to be rocked upon operation of the presser footlifting mechanism of the sewing machine, which is of the characterdisclosed in the Covert US. Pat. No. 2,977,910, granted Apr. 4, 1961.This will serve to rock the shaft 35 in a clockwise direction as it isseen in F IG. I and in a counterclockwise direction as it is seen inFIG. 6. As shown in the latter figure the rocking of the lever 40 in acounterclockwise direction about the pivot pin 41 will draw downwardly apin 42 which has a collar 42a adjustably secured thereto. The downwardmovement of pin 42 with its collar 42a will cause the latter to engagethe arm 38a of member 38 and force iitaway from the stop pin 45. Theresulting rocking movement of the lever 38 will, by virtue of its fixedconnection with the rock shaft 35 through the action of the screw 39cause counterclockwise movement of a member 46 that is adjustablyconnected with the lever 38 by means of a screw 460. Such rocking of thelever 46 will cause upward move ment of a pin 47 that is normally urgeddownwardly by a spring 48 (FIGS. 5 and 6). Upward movement of the pin 47will cause its upper end to engage the disk 12b and will lift thisagainst the action of spring 12a to release the frictional holding forcefrom the thread extending between the eyelets l1 and 13. Thus thetension applied to the thread will be released upon the lifting of thepresser foot. Also the rocking of the shaft 35 in the clockwisedirection in FIG. I will carry the guide members 14 and 15 away from theearns 30 and 31. This, of course, facilitates the removal of a finishedwork piece and the introduction of a new one. The parts referred to willbe restored to the position shown in FIG. 6 through the action of thesprings 44 and 48 when the presser foot is permitted to return intoengagement with the work support 1 of the frame. As shown in FIG. 6 thepin 42 is pivotally connected with the presser foot lifting lever 40 bya stud 43 having a screw threaded connection with the lever 40. As shownin FIG. 6, the pin 42 has a sliding engagement within an opening 38bprovided in the arm 38a of the lever 38. When the presser foot ispermitted to return to its engagement with the work support 1, thespring 44 will again rock the lever 38 in a clockwise direction (FIG. 6)until the arm 38a of the lever engages the stop pin 45. This will enablethe spring 48 to urge the pin 47 downwardly and thus cause the disk 12bto be forced downwardly by spring 120 to grip the thread passing betweenthe disks 12b and 120.

It will be understood that when work to be stitched is applied to thework supporting arm 1, the presser foot is lifted under manual control,either by hand or a foot treadle or a knee press, and then restored toits active position after the work has been properly positioned. Afterthe desired line of stitching has been provided on the work piece thepresser foot may be lifted again, and this frees the thread so that thework piece may be readily removed from the machine and the threadextending from the needle may be severed.

As shown in FIGS. 2 and 5, there is preferably provided a dust cover 70to protect against accumulation of any flying dust on the variouselements described above which are carried by the shaft 22 externally ofthe enclosed frame of the machine. This dust cover has a portion of thefree end of its cylindrical body fitted onto a slightly reduced diameterportion of the flange 24b of the member 24. A screw 71 may be providedfor retaining the cover 70 on the machine, this screw having threadedengagement with a hole 24d provided in the'flange 24b of the member 24.It will be understood that the cylindrical wall of the cover 70 willhave openings therein to permit the passage of the thread to and fromthe various elements described above which cooperate with the thread toimpart take-up and pull off actions thereto.

It is believed that the foregoing description of a preferred form of thepresent invention, as applied to a lock-stitch machine, serves to showhow the thread guiding and tensioning means functions to bring about aprecise control over the needle thread during high speed operations ofthe machine. Briefly, the thread from a supply source is first led to athread tensioning device having thread guiding means for directing thethread toward and away from a pair of thread gripping disks which areurged together under suitable spring force, which may be varied in aconventional manner, so that uniform movement of the thread is assured.From this thread tensioning device, shown at 12 in FIG. 3, the thread isled downwardly to an eyelet of an arm 14a of a member 14 and from heresuccessively through an arm 14b of member 14 and arms 15c, 15b and 15aof a member 15. In its passage between the various arms mentioned, thethread is subjected to a camming action by a series of cams 31b, 31a, b,300. From the eyelet in arm 15a the thread is passed toward the left(FIG. 3) and slightly downwardly to an eyelet l6 and then upwardly to athread take-up arm 17. From the eyelet in the latter it is passeddownwardly to the eye of the needle. The take-up arm 17 swings through asuitable are which imparts to the thread a desired takeup action, afterits loop has been passed half-way around the bobbin case of the rotaryhook 9. The coordination of the movements of the various elements whichapply a pulling force to the thread in the course of a stitch formingoperation is such as to prevent the accumulation of any large free loopor length of the thread between the various eyelets through which it isbeing shifted, and the application of an excessively high tension forceto the thread at any time during the operation of the machine isavoided. The cam elements 30a, 30b, 31a and 31b which contribute to thetake-up and pull-off action imparted to the thread, are so synchronizedas to avoid any sudden and excessive pull on the thread at any time, sothat puckering of the work being stitched is avoided and the desiredfirmness of the stitch is assured. However, the cam elements 30 doprevent the drawing of thread from the supply during the upward movementof the take-up arm 17 until the latter approaches its upper position.This insures the pulling of the thread out of the hook and up to theunderside of the work, after which the locking action on the threadeffected by the elements 30 is released and thread which has been drawnfrom the supply source by pull off earns 31 will be made available forstitch formation.

The length of thread that is pulled from the supply source during eachcycle of operation of the machine may be varied to create a tight orloose stitch. Such variation may be brought about by changing oradjusting the various cam elements used, or it can be brought about byadjusting the angular position of the members 14 and 15 to place theeyelets in the projections 14a, 14b, and 15a, 15b and 15c in a locationsuch as shown in FIGS. 1 and 4 which will enable the cam elements toexert the necessary pulling and locking action on the thread, at thetime it is needed. In connection with the thread control mechanism shownand described herein, it is believed to be clear that the cam elements31a and 31b serve to pull off most of the desired amount of thread fromthe supply cone C in the course of a stitching operation, while thetake-up 17 pulls off the remaining necessary thread as it reaches thetop of its stroke at the end of the stitch forming cycle. The camelements 30a and 30b serve to apply the desired high tension to thethread during a predetermined period of the stitch forming cycle. Thisresults from the location of the elements mentioned in relation to thepath of movement of the thread from its source to the stitch formingregion.

The operation of the various thread controlling and tensioning meansinvolved in this invention is so synchronized with the operation of thestitch forming elements as to avoid the presence of any length of freethread which may become entangled and form a knot in itself, as it mightdo if allowed to form a hanging loop. Also the invention insuresapplying the thread, to the work being stitched, in a uniform manner andwithout causing puckering or other objectionable effects, regardless ofthe speed of operation of the machine. This is partly achieved by theaction of the take-up lever 17 which, for example, will quickly pull upthread from the rotary hook after a loop of the thread, which is passedaround the bobbin case, has reached the 6 oclock point. The desiredapplication of the thread to the work in forming a stitch, and thepulling of thread from the supply source to be available for the nextstitch, is brought about by the action of the various cam elements thathave been described. It has been found that the mechanism of the presentinvention serves to apply the stitching to the work in the desired form,regardless of the thickness and other characteristics of the work, andat all speeds at which the machine is operated. The various cam elements30 and 31 cooperate with the members 14 and 15 in such manner as tobring about this result, without the need for a check spring, such asthat designated 50d in the above-mentioned Hale et al. patent. Theabsence of any need for such a spring in the present constructionreduces the distance through which it is necessary to swing the eye ofmember 17. This in addition to its primary function, was previouslyrequired to compensate for the movement of the thread engaging portionof the check spring.

While the invention has been described in considerable detail inrelation to the illustrative embodiment, it will be understood thatvarious modifications may be made within the scope of the appendedclaims. Such modifications may encompass adaptation of certain featuresof the invention to sewing machines of types other than the one hereindisclosed.

What is claimed is:

1. Sewing apparatus comprising a machine having a reciprocatory needlebar carrying a needle, cooperating stitch forming means, a main driveshaft, connections from said shaft for reciprocating said needle bar anddriving said cooperating stitch forming means, a thread supply means,means for controlling the delivery of thread from said supply means tosaid needle comprising a control shaft rotated in synchronism with saiddrive shaft, clamping means operated by said control shaft for grippingthe thread and looking it against movement to prevent additional threadbeing delivered from the supply to the needle from the time the threadbegins to be pulled up by the cooperating stitch forming means until thetime that the stitch is set.

2. In sewing apparatus as set forth in claim 1, wherein said clampingmeans for locking the thread in position comprises cam means rotated bythe control shaft in timed relation to the cooperating stitch formingmeans.

3. In sewing apparatus as set forth in claim 1, wherein there are meansalso operated by said control shaft positioned between the clampingmeans and the thread supply for pulling off a predetermined amount ofthread from the supply during the period in which the thread is grippedby the clamping means.

4. Sewing apparatus comprising a machine having a reciprocatory needlebar carrying a needle, cooperating stitch forming means, a main driveshaft, connections from said shaft for reciprocating said needle bar anddriving said cooperating stitch forming means, a thread supply means,means for controlling the delivery of thread from said supply means tosaid needle comprising a control shaft rotated in synchronism with saiddrive shaft, a plurality of cam elements rotated by said control shaft,thread guiding means adapted to retain different portions of said threadin the paths of movement of said cam elements. there being only arockable eyelet carrying arm and stationary eyelet means in the path ofmovement of the thread from the region of said cam elements to the eyeof said needle.

5. Sewing apparatus comprising a machine having a reciprocatory needlebar carrying a needle, cooperating stitch forming means, a main driveshaft, connections from said shaft for reciprocating said needle bar anddriving said cooperating stitch forming means, a thread supply means,means for controlling the delivery of thread from said supply means tosaid needle comprising a control shaft rotated in synchronism with saiddrive shaft, a plurality of cam elements rotated by said control shaft,thread guiding means adapted to retain different portions of said threadin the paths of movement of said cam elements, certain of said camelements being arranged to cooperate with spaced apart portions of thethread, and other of said cam elements being arranged to cooperate witha single portion of I said thread in spaced relation to the firstmentioned portions of the thread.

6. In sewing apparatus as set forth in claim 5, said other of said camelements involving relatively adjustable members adapted to vary theduration of activity of said cam elements upon a cycle of operation ofthe machine.

.7. In sewing apparatus as set forth in claim 6, said certain of saidcam elements having a duration of activity upon a cycle of operation ofthe machine that is longer than the combined duration of the activity ofsaid other of said cam elements.

8. Sewing apparatus comprising a machine having a main drive shaft, aplurality of thread carrying elements arranged to cooperate to formstitches, connections from said shaft for operating said elements, meansfor controlling delivery of thread to one of said elements in apredetermined amount to insure its firm and uniform application to awork piece being stitched, said means comprising a device for applying amain tension to said thread in its path of movement from a supplysource, means providing a plurality of stationary eyelets through whichthe thread is passed from said device, a plurality of cams arranged forrotation in the region of said eyelets, each of said cams having anoutwardly extending portion adapted to engage the thread and apply aforce thereto, whereby a stitch is applied to the work piece under adesired force.

9. In sewing apparatus as set forth in claim-8, certain of said camsbeing adapted to pull thread from said supply source through said devicefor applying a main tension to said thread.

10. In sewing apparatus as set forth in claim 9, said device forapplying a main tension to said thread comprising a pair of disks, aspring urging one of said disks toward the other, and adjustable meansfor varying the force, of said spring. r

11. In sewing apparatus as set forth in claim 8, said cams being carriedby a shaft which is rotated at the same speed as themain drive shaft ofthe machine.

12. In sewing apparatus as set forth in claim 8, certain of said camsbeing adapted to pull thread from said supply source through said devicefor applying a main tension to said thread, and other" of said camsbeing adapted to apply a further tension to said thread and to deliversuccessive portions thereof to said one of said thread carryingelements.

13. In sewing apparatus as set forth in claim 8, said thread carryingelements comprising a reciprocatory needle and a rotary hook, said meansfor controlling delivery of thread serving to control the threaddelivery to said needle and serving to supply the amount of threadneeded to form a loop around the rotary hook and to then pull up saidloop to the underside of the work being stitched.

14. In sewing apparatus as set forth in claim 13, said means forcontrolling delivery of thread to said needle including a rockable armhaving an eyelet therein through which the thread is passed toward saidneedle, said arm serving to alternately provide and then takeup acertain length of thread that is sufiicient to enable said hook to carrya loop of thread around a bobbin case within said rotary hook.

15. In sewing apparatus as set forth in claim 14, certain of said camsbeing adapted to pull thread from a supply source to make it availableto form a stitch.

16. In sewing apparatus as set forth in claim 8, a presser foot which isspring urged downwardly against the work being stitched, manuallyoperable means for lifting said presser foot, and connections from saidmanually operable means for shifting said normally stationary eyeletsaway from said cams when the presser foot is lifted.

17. In sewing apparatus'asset forth in claim 16, said lifting of thepresser foot being arranged to release the main tension applied to thethread by said device 18. Sewing apparatus comprising a sewing machinehaving thread carrying stitch forming elements and means for controllingthe delivery of thread to at least one of said stitch forming elementsfrom a supply, said thread controlling means comprising first and secondmeans for applying variable tension to the thread, thread pull-offmeans, thread take-up means, said first thread tension applying meansbeing adapted to apply a predetermined, constant, tension to the threadthroughout a part of a stitch forming cycle, said second thread tensionapplying means being adapted to apply a considerably higher tension tothe thread through one portion of the stitch forming cycle andcompletely releasing this higher tension during the remaining portion ofthe stitch forming cycle, said second tension applying means beinglocated between said one of the stitch forming elements and said firsttension applying means in the path of delivery of the thread, saidthread pull-off means being adapted to pull off one portion of theamount of thread that is needed for forming a stitch, during the periodwhen said second thread tension applying means applies said hightension, said thread pull-off means being located between said first andsecond tension applying means in the path of delivery of the thread,said thread take-up means being adapted to pull off from a supply theremaining portion of the thread needed for forming a stitch, during theperiod in the cycle when said higher tension is released, 5

and said second tension applying means and said pulloff means beingadapted to engage the thread in successive order with the second tensionapplying means first and the pull-off means later.

19. In sewing apparatus as set forth in claim 18, said second tensionapplying means and said pull-ofi means being arranged to disengage thethread simultaneously.

20. In sewing apparatus as set forth in claim 18, said second tensionapplying means and said pulloff means each comprising cam meansinvolving at least one cam, said cam means being mounted for rotation ona common shaft driven by the main drive shaft.

21. in sewing apparatus as set forth in claim 20, said cams being formedwith outwardly extending portions arranged to engage the thread.

22. In sewing apparatus as set forth in claim 21, said outwardlyextending portions of said cams being of a larger peripheral length onthe tension applying cam means than on the pull-off cam means.

23. A method of controlling the delivery of thread to the needle of asewing machine having a thread carryl fffi, bliicit%%n;s2;%h%3sslaisigzit needle to carry its thread through the work intocooperation with the rotary loop taker, pulling the needle thread upfrom the loop taker after it has been passed around the thread carriedby thelatter, applying a high tension force to the needle thread as itis being pulled from a loop taker, releasing said high tension when theneedle thread has been pulled up to the work piece and the stitch isset.

24. A method as set forth in claim 23 in which thread is drawn from theneedle thread supply source during the application of a high tensionthereto, said thread so drawn being stored outside of the area in whichsaid thread is affected by the application of said high tension, andadding the thread so drawn from the needle thread supply when said hightension is released, and thereafter drawing further thread from saidsupply in preparation for the next stitch-forming cycle.

1. Sewing apparatus comprising a machine having a reciprocatory needlebar carrying a needle, cooperating stitch forming means, a main driveshaft, connections from said shaft for reciprocating said needle bar anddriving said cooperating stitch forming means, a thread supply means,means for controlling the delivery of thread from said supply means tosaid needle comprising a control shaft rotated in synchronism with saiddrive shaft, clamping means operated by said control shaft for grippingthe thread and locking it against movement to prevent additional threadbeing delivered from the supply to the needle from the time the threadbegins to be pulled up by the cooperating stitch forming means until thetime that the stitch is set.
 2. In sewing apparatus as set forth inclaim 1, wherein said clamping means for locking the thread in positioncomprises cam means rotated by the control shaft in timed relation tothe cooperating stitch forming means.
 3. In sewing apparatus as setforth in claim 1, wherein there are means also operated by said controlshaft positioned between the clampIng means and the thread supply forpulling off a predetermined amount of thread from the supply during theperiod in which the thread is gripped by the clamping means.
 4. Sewingapparatus comprising a machine having a reciprocatory needle barcarrying a needle, cooperating stitch forming means, a main drive shaft,connections from said shaft for reciprocating said needle bar anddriving said cooperating stitch forming means, a thread supply means,means for controlling the delivery of thread from said supply means tosaid needle comprising a control shaft rotated in synchronism with saiddrive shaft, a plurality of cam elements rotated by said control shaft,thread guiding means adapted to retain different portions of said threadin the paths of movement of said cam elements. there being only arockable eyelet carrying arm and stationary eyelet means in the path ofmovement of the thread from the region of said cam elements to the eyeof said needle.
 5. Sewing apparatus comprising a machine having areciprocatory needle bar carrying a needle, cooperating stitch formingmeans, a main drive shaft, connections from said shaft for reciprocatingsaid needle bar and driving said cooperating stitch forming means, athread supply means, means for controlling the delivery of thread fromsaid supply means to said needle comprising a control shaft rotated insynchronism with said drive shaft, a plurality of cam elements rotatedby said control shaft, thread guiding means adapted to retain differentportions of said thread in the paths of movement of said cam elements,certain of said cam elements being arranged to cooperate with spacedapart portions of the thread, and other of said cam elements beingarranged to cooperate with a single portion of said thread in spacedrelation to the first mentioned portions of the thread.
 6. In sewingapparatus as set forth in claim 5, said other of said cam elementsinvolving relatively adjustable members adapted to vary the duration ofactivity of said cam elements upon a cycle of operation of the machine.7. In sewing apparatus as set forth in claim 6, said certain of said camelements having a duration of activity upon a cycle of operation of themachine that is longer than the combined duration of the activity ofsaid other of said cam elements.
 8. Sewing apparatus comprising amachine having a main drive shaft, a plurality of thread carryingelements arranged to cooperate to form stitches, connections from saidshaft for operating said elements, means for controlling delivery ofthread to one of said elements in a predetermined amount to insure itsfirm and uniform application to a work piece being stitched, said meanscomprising a device for applying a main tension to said thread in itspath of movement from a supply source, means providing a plurality ofstationary eyelets through which the thread is passed from said device,a plurality of cams arranged for rotation in the region of said eyelets,each of said cams having an outwardly extending portion adapted toengage the thread and apply a force thereto, whereby a stitch is appliedto the work piece under a desired force.
 9. In sewing apparatus as setforth in claim 8, certain of said cams being adapted to pull thread fromsaid supply source through said device for applying a main tension tosaid thread.
 10. In sewing apparatus as set forth in claim 9, saiddevice for applying a main tension to said thread comprising a pair ofdisks, a spring urging one of said disks toward the other, andadjustable means for varying the force of said spring.
 11. In sewingapparatus as set forth in claim 8, said cams being carried by a shaftwhich is rotated at the same speed as themain drive shaft of themachine.
 12. In sewing apparatus as set forth in claim 8, certain ofsaid cams being adapted to pull thread from said supply source throughsaid device for applying a main tension to said thread, and other ofsaid cams being adapted to apply a further tension to said thread and todeliVer successive portions thereof to said one of said thread carryingelements.
 13. In sewing apparatus as set forth in claim 8, said threadcarrying elements comprising a reciprocatory needle and a rotary hook,said means for controlling delivery of thread serving to control thethread delivery to said needle and serving to supply the amount ofthread needed to form a loop around the rotary hook and to then pull upsaid loop to the underside of the work being stitched.
 14. In sewingapparatus as set forth in claim 13, said means for controlling deliveryof thread to said needle including a rockable arm having an eyelettherein through which the thread is passed toward said needle, said armserving to alternately provide and then take-up a certain length ofthread that is sufficient to enable said hook to carry a loop of threadaround a bobbin case within said rotary hook.
 15. In sewing apparatus asset forth in claim 14, certain of said cams being adapted to pull threadfrom a supply source to make it available to form a stitch.
 16. Insewing apparatus as set forth in claim 8, a presser foot which is springurged downwardly against the work being stitched, manually operablemeans for lifting said presser foot, and connections from said manuallyoperable means for shifting said normally stationary eyelets away fromsaid cams when the presser foot is lifted.
 17. In sewing apparatus asset forth in claim 16, said lifting of the presser foot being arrangedto release the main tension applied to the thread by said device 18.Sewing apparatus comprising a sewing machine having thread carryingstitch forming elements and means for controlling the delivery of threadto at least one of said stitch forming elements from a supply, saidthread controlling means comprising first and second means for applyingvariable tension to the thread, thread pull-off means, thread take-upmeans, said first thread tension applying means being adapted to apply apredetermined, constant, tension to the thread throughout a part of astitch forming cycle, said second thread tension applying means beingadapted to apply a considerably higher tension to the thread through oneportion of the stitch forming cycle and completely releasing this highertension during the remaining portion of the stitch forming cycle, saidsecond tension applying means being located between said one of thestitch forming elements and said first tension applying means in thepath of delivery of the thread, said thread pull-off means being adaptedto pull off one portion of the amount of thread that is needed forforming a stitch, during the period when said second thread tensionapplying means applies said high tension, said thread pull-off meansbeing located between said first and second tension applying means inthe path of delivery of the thread, said thread take-up means beingadapted to pull off from a supply the remaining portion of the threadneeded for forming a stitch, during the period in the cycle when saidhigher tension is released, and said second tension applying means andsaid pull-off means being adapted to engage the thread in successiveorder with the second tension applying means first and the pull-offmeans later.
 19. In sewing apparatus as set forth in claim 18, saidsecond tension applying means and said pull-off means being arranged todisengage the thread simultaneously.
 20. In sewing apparatus as setforth in claim 18, said second tension applying means and said pull-offmeans each comprising cam means involving at least one cam, said cammeans being mounted for rotation on a common shaft driven by the maindrive shaft.
 21. In sewing apparatus as set forth in claim 20, said camsbeing formed with outwardly extending portions arranged to engage thethread.
 22. In sewing apparatus as set forth in claim 21, said outwardlyextending portions of said cams being of a larger peripheral length onthe tension applying cam means than on the pull-off cam means.
 23. Amethod of contRolling the delivery of thread to the needle of a sewingmachine having a thread carrying needle and a cooperating threadcarrying rotary loop taker, which comprises the steps of causing theneedle to carry its thread through the work into cooperation with therotary loop taker, pulling the needle thread up from the loop takerafter it has been passed around the thread carried by the latter,applying a high tension force to the needle thread as it is being pulledfrom a loop taker, releasing said high tension when the needle threadhas been pulled up to the work piece and the stitch is set.
 24. A methodas set forth in claim 23 in which thread is drawn from the needle threadsupply source during the application of a high tension thereto, saidthread so drawn being stored outside of the area in which said thread isaffected by the application of said high tension, and adding the threadso drawn from the needle thread supply when said high tension isreleased, and thereafter drawing further thread from said supply inpreparation for the next stitch-forming cycle.